Electrodeposition process using a bipolar activating medium

ABSTRACT

A bipolar activating medium having a metallic surface through which protrudes a plurality of small, dynamically hard, nonconductive particles held in spaced relationship to one another is insulated from any direct electrical contacts and is continuously moved under pressure against a cathodic surface being subjected to electrodeposition of metal from aqueous or low boiling electrolytes. The dynamically hard particles repetitively contact the electrodeposit at extremely short time intervals generating new surface defect sites and increasing the areas available for nucleation while the surface of the activating medium in the zone adjacent the cathodic surface acts as an anode. As the activating medium moves, that portion which acted as an anode reverts to act as a cathode while a fresh portion of the activating medium becomes anodic as it approaches the cathodic workpiece. In the zone of influence of the anode, the activating medium picks up a deposit of metal and an equal amount of metal dissolves from the portion of the activating medium which is in the zone of influence of the cathode thereby insuring an adequate supply of metal ions immediately adjacent the cathodic workpiece.

United States Patent 3,338,807 8/l967 Clifford Primary Examiner-John H. Mack Assistant Examiner-R. J. Fay Attameysl-Iugh E. Smith and Herbert L. Gatewood ABSTRACT: A bipolar activating medium having a metallic surface through which protrudes a plurality of small, dynamically hard, nonconductive particles held in spaced relationship aqueous or low boiling electrolytes. The dynamically hard par- [72] Inventor Steve Eisner Schenectady, [21] Appl. No. 888,678 [22] Filed Dec. 29, 1969 [45] Patented Nov. 9, 1971 [73] Assignee Norton Company Troy, N.Y. Continuation-impart of application Ser. No. 718,468, Apr. 3, 1968, now abandoned Continuation-impart of application Ser. No. 863,509, Oct. 3, 1969, Continuation-inpart of application Ser. No. 863,499, Oct. 13,1969. 8

[54] ELECTRODEPOSITION PROCESS USING A BIPOLAR ACTIVATING MEDIUM 5 Claims, 4 Drawing Figs.

[52] US. Cl 204/35 R, 204/23, 204/36, 204/268, 204/DIG. 10 [51] Int. Cl C23j 5/50 [50] Field of Search 204/216, 217, 224, 225, 226, 100, 35, 36, 29, 14,15, 208, 209, 254, 268

[56] References Cited UNITED STATES PATENTS 1,721,949 7/1929 Edelman 29 4/DI G l 0 3 +3 4 77 33 I v -b t 1 4+ 1 f 1 12 if, 1*

1 i i g1 ticles repetitively contact the electrodeposit at extremely short time intervals generating new surface defect sites and increasing the areas available for nucleation while the surface of the activating medium in the zone adjacent the cathodic surface acts as an anode. As the activating medium moves, that portion which acted as an anode reverts to act as a cathode while a fresh portion of the activating medium becomes anodic as it approaches the cathodic workpiece. In the zone of influence of the anode, the activating medium picks up a deposit of metal and an equal amount of metal dissolves from the portion of the activating medium which is in the zone of influence of the cathode thereby insuring an adequate supply of metal ions immediately adjacent the cathodic workpiece.

PATENEBNOV 9 l9?! SHEET 1 [IF 2 PRACTKAL AND umrrme CURRENT DENSITY 1h1e157b2if'2'5' VOLTS STEV mv%non 7 BY ATTORNEY ELECTRODEPOSITION PROCESS USING A BIPOLAR ACTIVATING MEDIUM RELATED APPLICATIONS The present application is a continuation-in-part of my earlier copending applications, Ser. No. 718,468 filed Apr. 3, 1968 (now abandoned), Ser. No. 863,509 filed Oct. 3, 1969 and Ser. No. 863,499 filed Oct. 3, 1969.

FIELD OF THE INVENTION Electrodeposition of metal on another surface through electrochemical action, has been generally a slow process. Particularly, this has been true in the production of dense, smooth, compact platings from aqueous solutions containing dissolved salts of the metal to be deposited. The present invention relates to this general field of electrodeposition'and includes the specific fields of electroplating, electrowinning, electrorefining and electroforming.

DESCRIPTION OF PRIOR ART Many efforts have been made in the past to speed up such electrodeposition processes but these have, in the main, met with only limited success. The chief reason for this is the existence of a limiting current density for all aqueous metal plating baths, such limit being determined by the concentration, temperature, transport number of the metal ions, the thickness of the polarization layer at the cathode or surface being plated, and particularly by the local increase in current density at asperities formed on the surface deposit. Efforts to increase the limiting current density (and resultantly the speed of deposition) have generally revolved around changes in the type of anion, increase in the amount of metal ion concentration in the electrolyte the use of higher electrolyte temperatures, and solution agitation, including greatly increasing the flow rate of the electrolyte solution. These efforts have not solved the problem of increasing speed of deposition to any appreciable extent. This problem has been largely overcome by the activating process described and claimed in my aforementioned application, Ser. No. 718,468. However, the activating process is so rapid that depletion of the metal ions may in some instances presenta problem. It is to this specific problem that the present process addresses itself.

SUMMARY As in the aforesaid application, Ser. No. 718,468, the present invention is directed towards a process in which the current density is high compared with that of conventional processes, e.g., 20,000 amps per square foot vs. l amps per square foot for conventional tin plating, and in which the surface of the deposit is repetitively contacted at extremely short time intervals by what is termed herein as dynamically hard" particles. By this term is meant that the combination of the hardness of the particles, the contact pressure of the particles on the surface of the electrodeposit and the speed at which such particles are moving relative to the electrodeposit surface is such as to produce an action on such surface sufficient to mechanically activate the surface. Activating" the surface of the electrodeposit within the meaning of the present invention requires the generation of new surface defect sites through mechanically distorting the crystal lattice of the metal deposited. It is believed that the mechanism is rather complex and consists of several actions taking place essentially simultaneously. First, there is the new surface defect site generation resulting from distortion of the crystal lattice structure as mentioned above. This provides growth sites for many more asperities than would be the case absent this mechanical distortion. Additionally, any dominant asperities already formed are cut off or bent over and crushed by the dynamically hard particle contact. These two actions result in substantial elimination of the current robbing which takes place at the asperities formed in normal plating and is believed to be one of the major contributing factors to the ability to maintain high current densities for substantial periods of time while maintaining acceptable deposits with this process. Further, the action of the activating medium is believed to result in the removal or substantial diminution of the stagnant polarization layer overlying the electrodeposit surface'and to maintain a high concentration of metal ions adjacent such surface due to the pumping action of the activating medium which carries a supply of fresh electrolyte across the electrodeposit surface at a high flow rate. By the use of a specially constructed and disposed type of activating medium it is possible to still further increase the supply of metal ions adjacent the electrodeposit surface. As described in detail below, the activating medium receives an electrodeposit at one point in its path of move ment and then as it approaches the workpiece it gives up the metal ions from such electrodeposit thus enriching the electrolyte immediately adjacent the surface where a high concentration of metal ions is required.

The present process requires the use of a surface disturbing or activating medium having the characteristics of providing a plurality of small, dynamically hard, relatively inflexible, nonconductive particles held in substantially fixed, spaced relationship to one another and generally vertical to the surface receiving the deposit by a matrix or supporting member which also has at least the outer surface thereof formed of a conductive metal through which the said particles penetrate. The specific activating medium may be formed as described in US Pat. No. 3,377,264 to Bruce W. Duke et al., issued Apr. 9, 1968, or may be formed using an entirely metallic substrate in which the nonconductive particles are embedded by those techniques well known in the metal-bonded grinding wheel art. The process further requires relative motion during the deposition operation between the surface receiving the deposit and the activating medium. In addition, sufficient pressure is applied to said activating medium in a direction normal to the electrodeposit surface to cause mechanical distortion of the crystal lattice structure of the metal deposited thereon. The spacing of the particles and the speed of relative movement is such that the deposited metal surface above any given point on the cathode surface is contacted or influenced by a particle at extremely short time intervals, e.g., intervals in the range of 6.1Xl0' to 3.8Xl0" seconds. Fresh electrolyte is supplied to the zones of activated metal deposit at the same rate as the activating medium moves through the electrolyte bath through entrapment by those surfaces of the activating medium (which surfaces may be the edges of the particles) parallel with the electrodeposit surface. By virtue of the bipolar nature of the activating medium, additional metal ions are given off by the activating medium adjacent the electrodeposit surface and are available for deposit at the high rates engendered by the activation process.

Accordingly, the principal object of the present invention is the provision of a high speed electrodeposition process for-the deposition of metals on a conductive substrate. The term electrodeposition" is intended to cover not only submersion within a bath but also the provision of a continuous flood of electrolyte over the deposit surface during deposition external of the physical confines of the usual tank used as a bath.

DRAWINGS FIG. 1 illustrates graphically the increase in limiting current density achieved with the process of the present invention.

FIG. 2 is a schematic illustration of the process of the present invention showing a belt-type activating medium.

FIG. 3 illustrates schematically an application of the present process using a disc-type activating medium.

FIG. 4 illustrates diagrammatically a portion of a cross section of one type of activating medium useful in the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The process of the present invention requires the controlled application under pressure, both normal to and parallel with the electrodeposit surface, of a supporting metallic-surfaced matrix which supports in closely spaced relationship protruding therethrough a plurality of small, relatively inflexible, nonconductive particles. These particles are so positioned in the matrix as to contact the deposit forming on the cathode sur- 5 face. The cathode surface, itself, is normally covered during electroplating with a relatively stagnant layer of electrolyte which may be identified as the diffusion or polarization layer. The thickness of this layer, even at high flow rates of electrolyte or turbulent agitation of a plating bath, is at least 0.00] centimeters. Under application of the supporting matrix and associated particles according to the present invention, this polarization layer is repetitively removed or its thickness substantially diminished repetitively throughout the plating cycle. As described above, the process activates the electrodeposit surface by multiplying many times the number of nucleation sites on such surface and generating a controlled growth of a tremendous number of very short asperities which are repetitively restricted in vertical growth throughout the deposition cycle. The metal deposit reflects this action since photomicrographs of the cross sections of such deposits illustrate a structure in which the growth axis of the crystals appears substantially parallel to the substrate rather than showing the normal columnar vertical orientation of conventional electrodeposits. This technique has been found to increase the limiting current density many times beyond that possible with other methods, resulting in much more rapid metal deposition than is possible with such other methods. The present method has further been found to produce a hard, dense, smooth metal deposit. These results are achieved even though practical application of the process may result in minor metal removal from the deposit on the cathode surface, cutting down slightly the total thickness of such deposit. This metal removal is minimized by control of the pressure applied td the activating medium but in order to insure adequate activation of the surface it is necessary to apply suffieient pressure to produce a light scratch pattern in the metal deposit. Thus, the dynamic hardness of the particles may be substantially greater than the actual hardness, e.g., a resin particle may produce a scratch in a much lharder nickel deposit. This scratch pattern may be visible to the naked eye but, in any case, will be seen under a magnification of 10,000 power or less. While the scratches may be produced by metal removal, preferably the dynamic hardness is so controlled that a displacement of metal atoms on the surface rather than actual removal is the basis for the scratch formation.

By using small, relatively inflexible, nonconductive particles as the activating tool, no spot on the deposit surface is covered for any appreciable length of time by the activating particle. Further, since the activating particles are fixed to the supporting matrix, there is no danger ofa particle being occluded as a erackinitiating impurity in the electrodeposit. These particles are generally randomly distributed over the cathode surfacecontactinlg side of the matrix and are preferably spaced in fixed relation to one another over very short spans, e.g., l.25 l0 inches to 5.65Xl0 inches. If desired, accurate and nonrandom distribution of the particles on the supporting matrix can be resorted to although this is generally an un- 60 necessary complication. By the term particle as is used herein is meant not only completely separate and discrete three-dimensional bodies, but also larger bodies with a plurali- 'ty of points, tips, projections or the like thereon as for instance a relatively hard resinous coating on a fiber wherein the coat- (.5 ing contains multiple irregular spaced projections and is generally uneven in nature. The particles, as described herein, contact or at least influence essentially all of the surface of the electrodeposit and are believed to knock down or cut off as they form most of the dominant asperities on such surface. The particles themselves may vary widely in size from l inches to l.25 l0 inches (average diameter) for example, but should generally be in the size range of from 9X10 inches to 2 l0 inches for best results. The particles can generally be defined as hard, i.e., having a Khoop hardness in excess of 10.0, but the degree of hardness per se is not critical except that control should be exercised not to use a product which is too abrasive for the particular metal being deposited. The degree of pressure applied must also be considered with respect to the hardness of the particles and generally with the softer range of particles more pressure normal to the cathode surface is required than with the harder range of particles.

As indicated above, the controlling factor is the dynamic hardness of the particles, i.e., the apparent hardness resulting from a combination of the actual Knoop hardness, the pressure applied and the speed with which the particles are moved across the electrodeposit. A visible indication that the dynamic hardness is sufficiently high is the presence in the deposit of the scratches visible under 10,000X magnification.

The nonconductive particles, as indicated above, are embedded in or at least protrude. through a metallic surface on the matrix. While the matrix may be entirely metal, it is.

preferred for use in belt form that a flexible woven textile backing coated with metal as described in the aforesaid US. Pat. No. 3,377,264 be used. The outer surface 17 of the activating medium must be composed of the metal which is to be deposited at the cathode in order to obtain proper operation in the initial startup of the process. This outer surface may be superposed, if desired, on a metal of different composition. lf the underlying metal is less noble than the metal to be deposited, such underlying metal must be protected from contact with the electrolyte. If the underlying metal is more noble than the surface metal to be deposited, no such precaution is necessary as the surface metal will dissolve preferentially. The metal to be deposited must, of course, be capable of dissolving under applied anodic current in the electrolyte to be used.

The most graphic effect, of the present process is the increase in practical limiting current density achieved. As is well known, the current density is directly related to the speed of metal deposit. The limiting current density is achieved when the application of increased voltage ceases to result in any substantial increase in current flow. As illustrated in FIG. 1 of the drawings, this curve will turn up again sharply at higher voltage but this is due to other reactions at the cathode, e.g., dissociation of water, etc. While interesting, this limiting current density is not necessarily a practical measure of plating rate since useful metal deposit in conventional electrodeposition processes will stop at a level below the limiting current density (practical current density). In the present process, not only is the limiting current density also the practical current density, but such current density is substantially above: the limiting current density for conventional processes. Referring to FIG'. 1, a plot of current density vs. voltage is shown. The lower curve shown in dotted lines is the plot of current density vs. voltage for an electroplating system for nickel using conventional techniques. Using exactly the same system but incorporating the activating process described herein results in the solid line curve shown in FIG. 1. It is apparent that the present process which gives both a practical and a limiting current density at 4,020 amps/ft. 2 is far above the practical current density of 385 amps/ft. and the limiting current density of 792 amps/ft. of the conventional process. It is equally apparent that metal ions are rapidly depleted from normal solutions by this aetivation'type deposition and that presence of adequate quantities of metal'ions adjacent the activated surface is a necessity.

Referring again to the drawings, FIG. 2 is a schematic plan view of the process of the present invention using a belt-type activating medium. The electrolyte 11 in container 10 may be any of the conventional plating solutions known to the art. Positioned in the electrolyte is an anode 12 of the metal which it is desired to electrodeposit and a cathode 13 connected to a conventional power source. The cathode 13 is the member to be plated and that portion thereof which it is desired to plate is suspended in the electrolyte bath l0. Adjacent to the face 14 of the cathode 13 to be plated is the activating member 15. As illustrated, this is a continuous belt 16 having a conductive metal face 17 through which protrude a plurality of small,

hard, nonconductive particles 18 adhered to the belt 16 by a suitable adhesive or anchored by embedment in the metal face 17. Belt 16 is mounted for rotation on a pair of pulleys l9 l9 driven in the direction shown by the arrow by a suitable motor (not shown). Pulleys 19-19 and belt 16 will be seen to be free of any direct electrical connection to the rest of the system. However, the metal of the belt is in dynamic equilibrium with the metal ions of the electrolyte, i.e., ions from the solution are constantly depositing as metal on the belt surface and metal from the belt surface is constantly dissolving to ions in the electrolyte. At equilibrium the rates of these two processes will be the same and no net change in the mass of the belt occurs. This interchange and the very low electrical resistance of the metal of the belt determines the electrical potential of the belt in the absence of external connections to sources of electrical potential. This potential must be substantially the same in all positions of the metal of the belt. The rate of dissolution of metal from the belt surface depends only on this potential while the rate of deposition of metal on the belt surface depends both on potential and on the local concentration of ions near the metal surface. Therefore, as the dissolution of anode 12 produces a local excess of metal ions, that portion of the metallic surface 17 of belt 16 in Zone A adjacent anode l2 experiences a local increase in concentration as these ions reach it by diffusion. This increase causes an increase in the local rate of deposition of metal ions without any I corresponding increase in the dissolution rate of the belt producing a net increase in the mass of metal 20 on this portion of the belt. Simultaneously a local deficiency of metal ions in the electrolyte of Zone B adjacent cathode 13 occurs because of their deposition as metal on cathode 13. This causes a decrease in the rate of deposition of such ions on the metal surface of the belt in Zone B and, since the rate of dissolution of ions from the metal surface remains constant, that portion of the belt in Zone B suffers a net decrease in the mass of metal on its surface equivalent to that gained by the portion of the belt in Zone A. The dissolution takes place in the spaces between the particles 18 where entrapped electrolyte is being carried rapidly across the face of the desired electrodeposit 21 on face 14 of cathode 13. As described above, the particles 18 contact and activate the surface of the electrodeposit 21 as they pass by it. As the belt rotates, the deposit formed on any given portion as it moves through Zone A is removed as that portion of the belt passes through Zone B. A steady state results in which that portion of the belt leaving Zone A at any given time is always slightly thicker than that portion which at such time is exiting from Zone B. However, this difference in thickness, while somewhat exaggerated in the drawing for purposes of illustration, is sufficiently small as to avoid any difficulty in rotation of the belt.

Referring now to FIG. 3 of the drawings, the electrolyte 31 in container 30 may be any of the conventional plating solutions known to the art. Positioned in the electrolyte 31 is an anode 32 of the metal which it is desired to electrodeposit and a cathode 33 connected to a conventional power source. The cathode 33 is the member which it is desired to plate and surface 34 thereof is the surface to be plated. Adjacent to the face 34 is the activating member 35. As illustrated, this is a metal disc 36 having a plurality of spaced, small, hard, nonconductive particles 37 anchored to one face thereof by a metal layer 38 deposited on the metal disc by sintering, brazing or the like. As shown, the tips of the particles 37 protrude through and extend above the metal layer 38. Disc 36 is mounted for rotation (in the direction shown by the arrow) on a suitable shaft 39 extending into container 30 through fluidproof bearings and seals 40 and connected to a conventional drive means (not illustrated). Positioned centrally of the disc 36 and extending outwardly from the particle-carrying surface thereof with which it is in contact is an insulating separator member 41. This member should be flexible enough to substantially conform to the surface of the particle-studded disc 36 so that as the disc rotates the separator 41 remains in contact with the surfaces of the particles 37. Due to the presence of the insulating separator member 41 the ions removed from the anode 32 are kept in Zone A in the vicinity of the anode and flow adjacent to the surface 38 of disc 36. That portion of disc 36 in Zone A at any given time will consequently acquire a deposit 42 as described above in connection with the belt in FIG. 2. As the disc rotates, that portion which has received the metal built-up in Zone A passes into Zone B where the metal 42 deposited in Zone A dissolves, again as described for the belt in FIG. 2, to enrich the metal ion concentration of the electrolyte 31 adjacent the desired electrodeposit 43 on the surface 34 of cathode 33. As indicated above, the activation of the surface of the deposit 43 by particles 37 results in a very rapid deposition rate. The ions given off by the bipolar activating medium 35 supplement those carried into contact with the surface of electrodeposit 43 in the spaces between the particles 37 on the rapidly rotating disc 36 in the form of entrapped electrolyte. This deposition and dissolution cycle continues for so long as the process is continued.

FIG. 4 shows a highly enlarged and idealized portion of one type of activating media suitable for use in the present invention and illustrates the hard particle-connecting metalfaced matrix relationship. Reference numeral 51 represents a nonconductive woven backing member having a plurality of small, hard, discrete, nonconductive particles 52 bonded to the surface thereof by an electrolyte-resistant adhesive 53. Overlying the adhesive layer 53 is an electrically conductive foil layer 54 adhered to adhesive layer 53. The tips of the nonconductive particles 52 extend through the foil layer 54. Also illustrated is a further modification over the products illustrated in FIGS. 2 and 3 which may be utilized to improve electrolyte flow. This consists of a plurality of perforations 55 which extend entirely through the backing 51 and both the adhesive layer 53 and the foil layer 54.

In operation, the present process is continuous and generally will eliminate the need of replenishing metal salts in the bath since the stationary active metal anode is the source of supply for metal ions. Regardless of the form of the bipolar activating medium, i.e., disc, belt, drum or the like, so long as it is face-conductive it will operate as a cathode while in the vicinity of the stationary anode and will accept a deposit of metal ions on its surface, which ions are then given up to the electrolyte (and hence are available for plating out on the cathodic workpiece) as the plated portion of the activating medium moves into the influence of the cathodic workpiece. Because the gap between the bipolar activating medium (now functioning as an anode) and the cathode workpiece is very smallspaced only by the tips of the nonconductive particlesthe rate of deposit or departure of the newly deposited ions from the bipolar anode surface is very rapid. The surface of the bipolar activating medium as it leaves the cathodic workpiece will generally be completely free from the electrodeposit it had carried into the zone of influence of the cathode and such surface is hence ready to receive a new deposit as it again passes into the influence of the anode.

The present invention is applicable to the electrodeposition of all metals conventionally deposited. It appears particularly of interest in the electrodeposition of Ni, Cu, Sn and A1 from aqueous solutions. However, the electrolyte system may be a nonaqueous, low boiling type if so desired. The type of movement of the activating media over the surface of the cathode may be varied widely, i.e., it may be linear as well as rotative; it may be a combination of movements, e.g., a rotating device which is also oscillated as it rotates, etc. The only requirement is that there be relative motion between the two of the order of magnitude herein described and claimed and that portions of the activating media be sequentially adjacent the anode and the cathode. While generally illustrated in connection with a soluble anode of the metal to be deposited, an insoluble anode may be used if desired. Simultaneous wiping of the anode as well as the electrodeposit surface with the activating medium can also be utilized if desired. Activation of the anode has been found to increase the rate of anode dissolution and to prevent the buildup of anode slimes. In some instances, activation of the anode alone or at a difierential rate by this process may be desirable.

The bipolar activating media described herein may likewise be varied widely, both in-shape or configuration and in composition. The requirements of the metal-surfaced supporting members and associated dynamically hard, nonconductive particles has been discussed in detail above. So long as the particles extend through the metal surface and the activating media is not electrically connected to the anode or cathode, the body of the activating media may be either metallic or nonmetallic. The nonconductive particulate activating materials likewise are noncritical in that many materials such as resin particles, abrasive grain, ceramic particles, glass particles, walnut shells or the like can be utilized.

The electrolyte is preferably held at ambient or room temperature e.g., 20 C., but can be used at temperatures up to the boiling point of the respective electrolyte used in a given setup.

The pressure of the activating medium on the electrodeposit surface, which as indicated above is variable depending on the particular activating particle used and the system in which it is used, may either be held relatively constant throughout any given deposition operation or varied, as desired, during the operation within the limits set by the requirement of the development of the aforementioned scratch pattern and the practical limit set by removal of undue amounts of metal.

I claim:

1. In a process for the high speed electrodeposition of metal from a system having an anode, a cathode and an electrolyte therebetween, the improvement which comprises providing a moving surface between but electrically insulated from said anode and said cathode, imposing a current flow between said anode and said cathode, simultaneously electrodepositing metal from said electrolyte onto said moving surface adjacent said anode and simultaneously dissolving metal from said surface into said electrolyte adjacent said cathode while discontinuously mechanically activating the surface of the electrodeposit forming on said cathode at extremely short repetitive time intervals throughout the period of electrodeposition.

2. A process as in claim 1 wherein the mechanical activation of the electrodeposit surface is by contact between said electrodeposit and said moving surface.

3. A process as in claim 2 wherein said moving surface is a conductive, metal-faced matrix supporting a plurality of spaced nonconductive activating particles secured in spaced relationship one from the other to said matrix and extending through the metal facing thereof.

4. A process as in claim 3 wherein the activating particles have a dynamic hardness sufficient to produce a scratch in said electrodeposit visible under magnification of 10,000 power.

5. A process as in claim 3 wherein the activating particles and the matrix function to carry quantities of fresh electrolyte over the surface of the electrodeposit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 r 619 r Dated November 9 1 71 Inventor(g) Steve Eisner It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, line 41 change "6.1 x 10 to 3.8 x 10 to read -6.1 x 10- to 3.8 x 10' Col. 3, line 56, change "1.25 x l0 inches to 5.65 x 10 to read --1.25 x 10- inches to 5.65 x 10' Col. 3, line 69, change "1 x 10 to read -l'x l0 Col. 3, line 70, change "1.25 x 10 to read --1.25 x 10- Col. 3, line 71, change "9 x 10 to read -9 x l0 Col. 3, line 72, change "2 x 10 to read -2 x l0' Col. 5, line 17, change "positions" to read -portions-.

Signed and sealed this 9th day of May 1972.

(m AL) A I, be .2: i; 2

EDWARD M.FLETCHER ,JR. ROBERT GOTTSCHALK Attes ting, Officer Commissioner of Patents )RM PO-1050 (10459) USCOMM-DC wave-P69 9 U 5 GOVERNMENT PRINTING OFFICE I969 OJii-334 

2. A process as in claim 1 wherein the mechanical activation of the electrodeposit surface is by contact between said electrodeposit and said moving surface.
 3. A process as in claim 2 wherein said moving surface is a conductive, metal-faced matrix supporting a plurality of spaced nonconductive activating particles secured in spaced relationship one from the other to said matrix and extending through the metal facing thereof.
 4. A process as in claim 3 wherein the activating particles have a dynamic hardness sufficient to produce a scratch in said electrodeposit visible under magnification of 10,000 power.
 5. A process as in claim 3 wherein the activating particles and the matrix function to carry quantities of fresh electrolyte over the surface of the electrodeposit. 